Hello again, Bea here, and welcome back to Biology!
We are getting ready to start our unit on cells. We've used the word "cell"
a few times already, but we haven't actually defined what a cell is yet.
You may already know that living things are made of cells. But what are cells made of?
Remember all those molecules you just finished learning about in the previous unit? Well,
cells are made of molecules, and hopefully you also remember that molecules are made of atoms.
So, we could also say that living things are made of atoms. An average human cell
contains trillions of atoms, and your body contains trillions of cells. That means
you have around 7 octillion atoms in your body! Want to understand just how big that number is?
Imagine all the grains of sand on earth. Now imagine all the grains of sand on a
million earths. That's 7 octillion grains of sand. That's how many atoms you have in your body. Being
organized into cells will make those 7 octillion atoms a little easier to keep track of. In today's
lesson, we'll take a very quick look at some of the topics we'll be exploring in this unit.
Have you ever used a microscope or seen one?
If you look at samples of living things under a microscope, you might see something like
one of these. Here you can actually see cells from four very different types of
organisms. Any guesses which ones are from a human? These are human nerve cells. What
about the others? We have some bacteria cells, plant cells, and some single-celled parameciums.
We'll spend quite a bit of time in this unit comparing different types of cells. Do you
see any similarities or differences here between bacteria, plant, and animal cells?
They are definitely different shapes, and we'll learn that they are actually
very different in size as well. Notice anything about what is inside the cells?
Some pieces are the same, but some are different too. No matter what kind of organism they are
a part of, cells have the very important job of keeping the organism alive. They transfer
materials, like oxygen and water, into and out of the cell. In the case of animal cells,
they allow our bodies to obtain energy from the food we eat. They tell our heart to keep pumping
and our lungs to keep breathing, and they contain important genetic information that can be passed
on to new cells. Plant cells have a superpower that allows them to turn sunlight into food.
We'll learn about how the structure of cells makes all of these jobs possible, and along the way,
we'll look at how our understanding of cells has changed over the last few centuries.
It's taken the work of many scientists to build the body of knowledge we now have about cells.
And more scientists will be needed in the future to keep building that knowledge.
Understanding cells and how they function is the key to curing and treating many
medical conditions. Maybe you'll be the one to help make the next breakthrough!
As you go through the unit, don't forget to complete the activities in the PDFs after
each video. These pages have additional information about the topic of the lesson,
as well as activities and experiments to complete. You will need the information
from these activities to successfully complete the assessments for each lesson.
The PDF that you will find attached to this lesson has all of the PDF materials for the whole unit.
Don't worry, there is nothing you need to complete in the PDF for this video. Just download the PDF
or print it out so that you have it ready for the rest of the unit. If you do forget,
or your pages get lost, you can also find the PDF for each individual lesson after the lesson video.
I can't wait to start telling you all about cells! Until then,
remember that biology isn't just science — it's the way of life!